A transmission detector for a window body, and a cleaning device for a viewing area of the window body are referred to in German Patent Application No. 197 49 331. A sensor array, situated on the base of an interior mirror of a motor vehicle, parallel to the exterior surface of its windshield, operates there as a position-sensitive optical detector for detecting objects, e.g., rain droplets on the exterior of the windshield. The sensor array covers only a small section of the windshield. Influencing factors on the transmission of the windshield which do not evenly affect the entire windshield surface may thus be detected either with relatively great uncertainty or not at all.
Another transmission detector and a cleaning device equipped with it are referred to in German Patent Application No. 199 43 887. Here, the radiation, emitted from a relatively small section of a windshield of a motor vehicle, is utilized with the aid of a position-insensitive detector for transmission detection. In addition to the disadvantages mentioned, due to the coverage of only a small section of the window body, additional limits may arise here due to the fact that, by using such a transmission detector, it cannot be determined which type of effect, e.g., which type of object on the windshield, has triggered the transmission change of the window body.